How is malignant mesothelioma diagnosed?
Mesothelioma is most often diagnosed after a person goes to a doctor because of symptoms. If there is a reason to suspect you might have mesothelioma, your doctor will use one or more tests to find out. Symptoms might suggest that the problem could be mesothelioma, but tests are needed to confirm the diagnosis.
Signs and symptoms of mesothelioma
Early symptoms of mesothelioma are not specific to the disease, so at first people may ignore them or mistake them for common, minor ailments. Most people with mesothelioma have symptoms for at least a few months before they are diagnosed.
Symptoms of pleural mesothelioma (mesothelioma of the chest) can include:
- Pain in the lower back or at the side of the chest
- Shortness of breath
- Weight loss
- Trouble swallowing
- Swelling of the face and arms
Symptoms of peritoneal mesothelioma can include:
- Abdominal (belly) pain
- Swelling or fluid in the abdomen
- Weight loss
- Nausea and vomiting
The symptoms and signs above may be caused by mesothelioma, but they are more often caused by other conditions. Still, if you have any of these problems (especially if you have been exposed to asbestos), it's important to see your doctor right away so the cause can be found and treated, if needed.
Medical history and physical exam
If you have any signs or symptoms that suggest you might have mesothelioma, your doctor will want to take a complete medical history to learn about your symptoms and possible risk factors, especially asbestos exposure. You will also be asked about your general health.
A physical exam can provide information about possible signs of mesothelioma and other health problems. Pleural mesothelioma can cause fluid to build up around the lungs in the chest (called a pleural effusion). In cases of peritoneal mesothelioma, fluid can build up in the abdomen (called ascites). In pericardial mesothelioma, fluid builds up in the sac around the heart (called a pericardial effusion). Rarely, mesothelioma can develop in the groin and look like a hernia. All of these might be found during a physical exam, such as when the doctor listens to these areas with a stethoscope.
If mesothelioma is a possibility, tests will be needed to make sure. These might include imaging tests, blood tests, and other procedures.
Imaging tests use x-rays, radioactive particles, or magnetic fields to create pictures of the inside of your body. Imaging tests may be done for a number of reasons, including to help find a suspicious area that might be cancerous, to learn how far cancer may have spread, and to help determine if treatment has been effective.
This is often the first test done if someone has symptoms such as a constant cough or shortness of breath. It may show an abnormal thickening of the pleura, calcium deposits on the pleura, fluid in the space between the lungs and the chest wall, or changes in the lungs themselves as a result of asbestos exposure. These findings could suggest a mesothelioma.
Computed tomography (CT) scan
The CT scan is an x-ray test that produces detailed cross-sectional images of your body. Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around you while you are lying on a narrow table. A computer then combines these into images of slices of the body. Unlike a regular x-ray, a CT scan creates detailed images of the soft tissues in the body.
CT scans are often used to help look for mesothelioma and to determine the exact location of the cancer. They can also help stage the cancer (determine the extent of its spread). For example, they can show whether the cancer has spread to other organs. This can help to determine if surgery might be a treatment option. Finally, CT scans can be used to learn whether treatment such as chemotherapy has been helpful in shrinking or slowing the growth of the cancer.
Before any pictures are taken, you may be asked to drink 1 to 2 pints of a liquid called oral contrast. This helps outline the intestine so that certain areas are not mistaken for tumors. You may also receive an IV (intravenous) line through which a different kind of contrast dye (IV contrast) is injected. This helps better outline structures in your body. The injection can cause some flushing (redness and warm feeling). Some people are allergic and get hives or, rarely, more serious reactions like trouble breathing and low blood pressure. Be sure to tell the doctor if you have any allergies or have ever had a reaction to any contrast material used for x-rays.
CT scans take longer than regular x-rays. You need to lie still on a table while the scan is being done. During the test, the table slides in and out of the scanner, a ring-shaped machine that completely surrounds the table. You might feel a bit confined by the ring you have to lie in while the pictures are being taken. Spiral CT (also known as helical CT), which is now used in many medical centers, uses a faster machine that reduces the dose of radiation and gives more detailed pictures.
Positron emission tomography (PET) scan
For a PET scan, a radioactive substance (usually a type of sugar related to glucose, known as FDG) is injected into the blood. The amount of radioactivity used is very low. Because cancer cells in the body grow quickly, they absorb more of the sugar than most other cells. After waiting about an hour, you lie on a table in the PET scanner for about 30 minutes while a special camera creates a picture of areas of radioactivity in the body.
The picture from a PET scan is not finely detailed like a CT or MRI scan, but it can provide helpful information about whether abnormal areas seen on these tests are likely to be cancerous or not. For example, it can give the doctor a better idea of whether a thickening of the pleura or peritoneum seen on a CT scan is more likely cancer or merely scar tissue. If you have been diagnosed with cancer, your doctor may use this test to see if the cancer has spread to lymph nodes or other parts of the body. A PET scan can also be useful if your doctor thinks the cancer may have spread but doesn't know where.
Some machines are able to do both a PET and CT scan at the same time (PET/CT scan). This lets the doctor compare areas of higher radioactivity on the PET scan with the more detailed appearance of that area on the CT.
Magnetic resonance imaging (MRI) scan
Like CT scans, MRI scans provide detailed images of soft tissues in the body. But MRI scans use radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed and then released in a pattern formed by the type of body tissue and by certain diseases. A computer translates the pattern into very detailed images of parts of the body. A contrast material called gadolinium is often injected into a vein before the scan to better show details.
MRI scans can sometimes help show the exact location and extent of a tumor since they provide very detailed images of soft tissues. For mesotheliomas, they may be useful in looking at the diaphragm (the thin band of muscle below the lungs that helps us breathe), a possible site of cancer spread.
MRI scans take longer than CT scans – often up to an hour. You may have to lie inside a narrow tube, which can upset people with a fear of enclosed spaces. Special, more open MRI machines may be an option in some cases. The MRI machine makes buzzing and clicking noises that you might find disturbing. Some places will give you earplugs to help block this out.
Blood levels of certain substances are often higher in people with mesothelioma:
- Soluble mesothelin-related peptides (SMRPs), detected with the MesoMark® test
Blood tests for these substances are not used to diagnose mesothelioma, but high levels may make the diagnosis more likely. Thus far, these blood tests have proven more useful in people who have already been diagnosed to follow their progress during and after treatment.
If mesothelioma is diagnosed, other blood tests will be done to check your blood cell counts and levels of certain chemicals in the blood. These tests can give the doctor an idea of how extensive the disease may be, and how well organs such as the liver and kidneys are working.
Tests of fluid and tissue samples
Symptoms and test results may strongly suggest that a person has mesothelioma, but the actual diagnosis is made by removing cells from an abnormal area and looking at them under a microscope. This is known as a biopsy. It may be done in different ways, depending on the situation.
Removing fluid for testing
If mesothelioma might be causing a buildup of fluid in the body, a sample of this fluid can be removed by inserting a thin, hollow needle through the skin and into the fluid to remove it. Numbing medicine is used on the skin before the needle is inserted. This may be done in a doctor's office or in the hospital.
This procedure has different names depending on where the fluid is:
- Thoracentesis removes fluid from the chest.
- Paracentesis removes fluid from the abdomen.
- Pericardiocentesis removes fluid from the sac around the heart.
The fluid is then tested to check its chemical makeup and is looked at under a microscope to see if it contains cancer cells. If cancer cells are found, special tests can tell whether the cancer is a mesothelioma, a lung cancer, or another type of cancer.
Not finding any cancer cells in the fluid does not always mean there is no cancer. Even when cancer is present, not all fluid will have cancer cells. In many cases, doctors need to get an actual sample of the pleural or peritoneal tissue to determine if a person has mesothelioma
Suspected tumors in the chest are sometimes sampled by needle biopsy. A long, hollow needle is passed through the skin in the chest between the ribs and into the pleura. Imaging tests such as CT scans are used to guide the needle into the tumor so that small samples can be removed to be looked at under the microscope. This is often done using just numbing medicine.
Needle biopsy can also be used to get samples of the lymph nodes in the space between the lungs to see if the cancer has spread there (see Endobronchial ultrasound needle biopsy).
Needle biopsies do not require a surgical incision or overnight hospital stay. But a possible downside is that sometimes the samples removed are not big enough to make an accurate diagnosis. If this happens, a more invasive biopsy method may be needed.
There is a slight chance that the needle could put a small hole in the lung during the biopsy. This can cause air to build up in the space between the lung and the chest wall (known as a pneumothorax). A small pneumothorax may cause no symptoms. It may only be seen on an x-ray done after the biopsy, and it will often go away on its own. But a larger pneumothorax can make part of a lung collapse, causing shortness of breath. If needed, this can be treated by placing a small tube through the skin and into the space for a short time. The tube is used to suck the air out in order to re-expand the lung.
An endoscope is a thin, tube-like instrument used to look inside the body. It has a light and a lens (or tiny video camera) on the end for viewing and often has a tool to remove tissue samples. Endoscopes have different names depending on the part of the body where they’re used. There are a number of different types of endoscopic biopsies.
Thoracoscopy: This procedure uses a thoracoscope to look at areas in the chest, including the pleura, and take tissue samples for biopsies. Thoracoscopy is done in the operating room while you are under general anesthesia (in a deep sleep). The doctor inserts the thoracoscope through one or more small cuts made in the chest wall to look at the space between the lungs and the chest wall. This lets the doctor see potential areas of cancer and remove small pieces of tissue to look at under the microscope. Thoracoscopy can also be used to sample lymph nodes and fluid and to assess whether a tumor is growing into nearby tissues or organs.
Laparoscopy: For this test, the doctor uses a laparoscope to look inside the abdomen and biopsy any peritoneal tumors. This is done in the operating room while you are under general anesthesia (in a deep sleep). The laparoscope is inserted into the abdomen through small cuts on the front of the abdomen.
Mediastinoscopy: If imaging tests such as a CT scan suggest that the cancer may have spread to the lymph nodes between the lungs, the doctor may want to remove some of them to see if they really contain cancer. This may be done during a procedure called a mediastinoscopy. This is also done in an operating room while you are under general anesthesia (in a deep sleep).
A small cut is made in the front of the neck above the breastbone (sternum) and a thin, hollow, lighted tube (called a mediastinoscope) is inserted behind the sternum. Special instruments can be passed through this tube to take tissue samples from the lymph nodes along the windpipe and the major bronchial tube areas.
Cancers in the lung often spread to lymph nodes, but mesotheliomas do this less often. Testing the lymph nodes can help show whether a cancer is still localized or if it has started to spread, which might affect treatment options. It can also sometimes help distinguish lung cancer from mesothelioma.
Bronchoscopy: This test does not require any cuts in the skin. It uses a bronchoscope – a long, thin, flexible, fiber-optic tube that is placed down the throat and into the lungs to look at the lining of the main airways. This procedure is done while you are asleep or sedated. If a tumor is found, the doctor can take a small sample of the tumor through the tube.
Endobronchial ultrasound needle biopsy: This type of biopsy may be done instead of a mediastinoscopy to get samples of the lymph nodes in the space between the lungs. It can help determine if surgery might be a treatment option. This procedure may be done with either general anesthesia (where you are asleep), or with numbing medicine (local anesthesia) and light sedation. A bronchoscope with an ultrasound device at its tip is passed down into the windpipe. It sends out sound waves and picks up the echoes to let the doctor view the nearby lymph nodes. A hollow needle is then passed down the bronchoscope and through the airway wall into the nodes to take biopsy samples.
Open surgical biopsy
Sometimes, more invasive procedures may be needed to get enough tissue sample to make a diagnosis. By making an incision in the chest (thoracotomy) or an incision in the abdomen (laparotomy) the surgeon can remove a larger sample of tumor or, sometimes, remove the entire tumor.
Testing the samples in the lab
No matter how they were obtained, all biopsy and fluid samples are sent to the pathology lab. There, a doctor will look at them under a microscope and test them to find out if they contain cancer cells (and if so, what type of cancer it is).
It is often hard to diagnose mesothelioma by looking at cells from the fluid around the lungs, abdomen, or heart. It can even be hard to diagnose mesothelioma with tissue from small needle biopsies. Under the microscope, mesothelioma can often look like other types of cancer. For example, pleural mesothelioma may resemble some types of lung cancer, and peritoneal mesothelioma in women may look like some cancers of the ovaries.
For this reason, special lab tests are often done to help tell mesothelioma from some other cancers.
Immunohistochemistry: This test looks for different proteins on the surface of the cells. It can be used to tell if the cancer is a mesothelioma or a lung cancer, which can sometimes appear to start in the inner lining of the chest.
DNA microarray analysis: This is a newer test that actually looks at patterns of genes in the cancer cells. Mesothelioma cells have different gene patterns than other cancer cells.
Electron microscopy: This can sometimes help diagnose mesothelioma. The electron microscope can magnify samples many more times than a normal light microscope. This more powerful microscope makes it possible to see the small parts of the cancer cells that can distinguish mesothelioma from other types of cancer.
If mesothelioma is diagnosed, the doctor will also determine what type of mesothelioma it is, based on the patterns of cells seen in the microscope. Most mesotheliomas are classified as either epithelioid, sarcomatoid, or mixed/biphasic.
Pulmonary function tests
If mesothelioma has been diagnosed, pulmonary function tests (PFTs) may be done to see how well your lungs are working. This is especially important if surgery may be an option to treat the cancer. Surgery often requires removing part or all of a lung, so it’s important to know how well the lungs are working to start with. These tests can give the surgeon an idea of whether surgery may be an option, and if so, how much lung can safely be removed.
There are a few different types of PFTs, but they all basically have you breathe in and out through a tube that is connected to a machine that measures your lung function.
Last Medical Review: 09/20/2012
Last Revised: 09/20/2012